A quantitative Scalar Timing Model is now available to explain temporal discrimination performance aggregated over trials and subjects. An objective of the present research is to develop a scalar timing theory that applies to individual trials of individual animals. Groups of 10 rats each will be trained in four different timing tasks that require the production of a single response after a fixed time, the production of repetitive responses at fixed intervals, the discrimination of the duration of a single stimulus or discrimination of the repetition interval between stimuli. The first major question is whether or not the model of temporal discrimination applies to individual animals rather than to tasks. If so, some of the parameter values should be constant across tasks but consistent across individuals. The second major question is to describe the characteristics of the internal clock used for duration discrimination. An attempt will be made to determine if there is an optimal pacemaker rate, to identify variables affecting this rate, and to determine whether an interval or periodic clock is used for duration discrimination in the second to minute range.